Time-series model for vehicle speeds

This paper presents a time-series model for the spot speeds of vehicles on a road section. Based on time-series analysis techniques, the model incorporates information on the extent of existing dependency between the speeds of successive vehicles. The model for the data is chosen while relying heavily on the data, and thus emphasis is given to their special characteristics. The advantages of using the model are examined with regard to the relative speed of two successive vehicles along a road section. The results are compared with those obtained by using a model of independent observations; fewer errors are obtained with the time-series model. Therefore, it is concluded that the sequence of speed observations contains valuable information which should be incorporated into speed models.

Flavone C-glycosides from Vaccaria pyramidata: Structure elucidation by spectroscopy and theoretical calculations

The flavone C-glycosides namely apigenin-7-O-β-D-glucopyranosyl-8-C-β-D-glucopyranoside (1) and apigenin-8-C-α-L-rhamnopyranosyl-(1→2)-O-β-D-glucopyranoside (2), along with p-methoxycinnamic acid (3), vaccaroside A (4), vaccaroside D (5), vaccaroside E (6) and abscisic acid glucose ester (7) were isolated from the methanol extract of the aerial parts of Vaccaria pyramidata. Structure elucidation of compounds 1-7 was accomplished by the extensive use of 1D- and 2D NMR experiments along with HR-ESI-MS. The structures of 1-2 have been confirmed by theoretical study of the 1H, 13C chemical shifts and UV data. In addition, Ionization Potential (IP) and Bond Dissociation Enthalpy (BDE) were used to evaluate the theoretical antioxidant activity of compounds 1 and 2. TD-DFT method (time-dependent density functional) was used to calculate the electronic absorption spectra of compounds 1 and 2 from optimized structures in methanol and the orbitals involved in the electronic transition were elucidated

Fingerprinting of strong spermatogenesis steroidal saponins in male flowers of <i>Phoenix dactylifera</i> (Date Palm) by LC-ESI-MS

<p>A fingerprint of steroid saponins, the major constituent in 80% methanolic fraction from the male flowers of <i>Phoenix dactylifera</i> has been established. Under ESI-MS/MS conditions, the fragmentation patterns of [M − H]⁻ ions exclusively displayed signals corresponding to the cleavage of the glycosidic bonds, thus allowing a rapid identification of 21 steroidal saponins. Moreover, two unique among them conjugated with histidine were detected by LC-ESI (-)-MS and DFT and were given tentative names of 3-<i>o</i>-histidine-26-<i>o</i>-hexosyl-dioscin and 3-<i>o</i>-histidine-26-<i>o</i>-dihexosyl-hydroxydioscin. Their steroidal saponins exhibited a significant improvement of the sperm cells count, motility and viability in male rats. These effects could be attributed to enhancing the levels of sex hormones.</p

Microbial biotransformation as a tool for drug development based on natural products from mevalonic acid pathway: A review

Natural products are structurally and biologically interesting metabolites, but they have been isolated in minute amounts. The syntheses of such natural products help in obtaining them in bulk amounts. The recognition of microbial biotransformation as important manufacturing tool has increased in chemical and pharmaceutical industries. In recent years, microbial transformation is increasing significantly from limited interest into highly active area in green chemistry including preparation of pharmaceutical products. This is the first review published on the usage of microbial biocatalysts for some natural product classes and natural product drugs